<html>

<head>

  <script src="zepto.js"></script>

</head>
<body>
  <div style="width:100px;height:100px;border:1px solid black"></div>
  <button>Click me</button>

  <script>
    $("div").html("Hello <b>Universe</b>!");
    $("div").on("mousedown",function(){ console.log("mousedown")})
            .on("mouseenter",function(){ console.log("mouseenter")})
            .on("mouseleave",function(){ console.log("mouseleave")});

    var counter = 0;

    $( "button" ).on( "click", function() {
      $( this ).text( `clicked ${ ++counter } times` );
    });



  </script>

</body>
</html>